1. Field of the Invention
The present invention relates to an ink-jet recording medium which can satisfactorily absorb inks and exhibits high print density, minimized bleeding with time, and satisfactory light resistance, and to an image forming method using the ink-jet recording medium.
2. Description of the Related Art
A variety of information processing systems have been developed with rapid expansion of the information technology industry, and recording methods and recording apparatus suitable for the information processing systems have been developed and have been in actual use.
Among these recording methods, an ink-jet recording method is widely used in “home use” as well as in office use, since the method can record information on a variety of recording materials and can use hardware (apparatus) that is available at relatively low cost, is compact and is quiet.
“Photographic” high-quality records can be obtained with an increasing resolution of ink-jet printers, and a variety of ink-jet recording mediums for use in such applications have been developed.
Such ink-jet recording mediums must generally: (1) dry quickly (absorb inks at a high speed), (2) form ink dots having a proper and uniform diameter without bleeding, (3) form ink dots which are satisfactorily particulate, (4) form ink dots with high circularity, (5) form images with high color density, (6) form images with high chromaticness without dullness, (7) carry a printing area with good water resistance, light resistance, and ozone resistance, (8) have a high degree of whiteness, (9) be stored satisfactorily, without yellowing or coloring even during long-term storage and without bleeding of images even during long-term storage, i.e., with minimized bleeding with time, (10) be resistant to deformation and have good dimensional stability with sufficiently minimized curling, and (11) pass through an apparatus smoothly.
When these ink-jet recording mediums are used in photo (glossy) paper to obtain “photographic” high-quality records, they must further have satisfactory glossiness, surface smoothness, and printing-paper-like feeling similar to silver halide film photos, in addition to the above properties.
To satisfy the above requirements, a variety of recording media have been proposed. For example, a proposal to improve absorption, color development and resolution can be found in Japanese Patent Application Laid-Open (JP-A) No. 02-276670, which discloses a recording medium comprising a support and a porous layer which is disposed on the support and contains inorganic particles such as aluminium hydrates. Another proposal can be found in JP-A No. 04-101880 which discloses a recording medium comprising a support, and an ink-fixing layer which is disposed on the support and contains a transparent resin that is dissolved in or swells with a solvent in an ink. Still another proposal can be found in Japanese Patent Application Publications (JP-B) No. 02-18146 and No. 02-31673, each of which discloses a recording medium comprising a support, and an ink receiving layer which is disposed on the support and contains any one of thermoplastic resin particles, emulsions and latices.
Separately, JP-A No. 09-99634 proposes a recording medium having an ink receiving layer comprising a polymer complex of a basic polymer and a styrene/(meth)acrylic acid copolymer. JP-A No. 09-156211 proposes a recording medium comprising a transparent support and an ink receiving layer which is disposed on the support and contains fine crosslinked polymer particles having an average particle diameter of 200 nm or less and a water-soluble resin. This sheet-like medium has a transmittance of 80% or more. JP-A No. 10-324053 proposes a recording medium having a porous film prepared from an emulsion containing a nitrite ester of carboxycellulose, and a film-forming aid.
These conventional recording media have improved ink absorbency or exhibit improved resolution, density, transparency and glossiness of the resulting images. However, even these recording media have some problems when they are subjected to high-speed printing of high-quality images equivalent to silver halide film photos, which technology has been achieved with the rapid-pace advance of recording apparatus.
For example, the recording medium disclosed in JP-A No. 02-276670 has a porous layer which contains inorganic particles such as aluminium hydrates, is disposed on its surface and exhibits satisfactory image quality and glossiness. However, the surface of the recording medium is brittle and thereby is readily damaged during transportation in some transportation systems of printers. In addition, this recording medium comprises organic particles and an organic resin in combination, has thereby low transparency and causes a shadow of the medium projected on a screen when it is used in transmitting systems such as overhead projector (OHP) films.
The recording medium disclosed in JP-A No. 04-101880 has an ink-fixing layer comprising a resin that is dissolved in or swells with a solvent in an ink. This recording medium exhibits a low drying speed of an ink and remains sticky for some time after recording. In addition, its ink-receiving layer does not have sufficient water resistance and invites migration of a dye due to moisture. The insufficient water resistance of the ink-receiving layer further invites cracks in printed areas, specifically in solid-printed areas, when a pigment is used as the ink.
The recording media disclosed in JP-B No. 02-18146 and JP-B No. 02-31673 comprise a support, and an ink receiving layer which is disposed on the support and contains any one of thermoplastic resin particles, emulsions, and latices. The recording media can absorb an ink at a high speed, but their ink absorbing property utilizes only voids among thermoplastic resin particles. Accordingly, to absorb sufficient amounts of inks, it must have an increased thickness of the ink receiving layer, thus inviting decreased transparency and strength of the film.
In the recording medium disclosed in JP-A No. 09-99634 having an ink receiving layer comprising a binder and organic particles, the ink receiving layer is formed from a polymer complex obtained by dissolving the binder and organic particles in a solvent and mixing the solution. The resulting ink-receiving layer does not have sufficient pores or voids and is thereby not promising for absorbing inks at a high speed.
The recording medium disclosed in JP-A No. 09-156211 has a transparent support, and an ink-receiving layer which is disposed on the support and comprises fine crosslinked polymer particles having an average particle diameter of 200 nm or less and a water-soluble resin. This recording medium cannot have sufficient voids among the fine particles, since it uses a water-soluble resin as a binder. In addition, it cannot significantly have an increased absorption speed by action of such voids, since it uses a relatively large amount of the water-soluble resin in a ratio of the water-soluble resin to the fine polymer particles of 1:1 to 1:10.
The recording medium disclosed in JP-A No. 10-324053 has a porous film formed from a film-forming aid and an emulsion containing a carboxycellulose nitrite and has voids among the emulsion particles. However, the porous film layer cannot be significantly controlled in its pH, and when pH is low and the film layer is acidic, a dye in an ink after printing peculiarly aggregates and thereby may exhibit a color different from its inherent color.
Consequently, ink-jet recording mediums that are capable of satisfactorily absorbing inks, exhibit high print density, minimized bleeding with time, and satisfactory light resistance and can print high-quality images equivalent to silver halide film photos at a high speed have not yet been provided, and demands on such improvements have been made.